1. Field of the Invention
The present invention relates to an on-vehicle generator mounting device and, more particularly, to a structure of a device for fixing and mounting an on-vehicle generator onto an engine of a vehicle.
2. Description of the Related Art
As an example of conventional on-vehicle generator mounting device, for example, a “mounting device for an on-vehicle generator” is disclosed in the Japanese Utility Model Publication (unexamined) No. 54747/1989.
Specifically, this Japanese Utility Model Publication (examined) No. 54747/1989 discloses “an on-vehicle generator mounting device including: a stay attached to an engine of a vehicle and having an insertion hole for mounting the generator onto an engine of the vehicle; a front bracket side mounting leg and a rear bracket side mounting leg of the generator both located on two sides of the stay; an insertion hole provided through one of the mounting legs; a cylindrical mounting-span-adjusting bush movably fitted into a fitting hole provided through the other mounting leg; a clamp nut accommodated in the other mounting leg adjacent to and coaxially with the mounting-span-adjusting bush, so as not to turn and get out, with a gap in radial direction; and a bolt inserted through the insertion hole of the other mounting leg, through the insertion hole of the stay and through the mounting-span-adjusting bush, the bolt being screw-engaged with the clamp nut.
Thus, the Japanese Utility Model Publication (examined) No. 54747/1989 discloses “anon-vehicle generator mounting device” in which a clamp nut is fitted into a mounting leg, which is fitted to and holds a mounting-span-adjusting bush of a generator, in such a manner as to be adjacent to the mounting-span-adjusting bush concentrically, unable to turn and get out, with a gap in radial direction.
It is a recent trend that an on-vehicle generator is reduced in weight under the need of lightweight vehicle.
Accordingly, in the field of an on-vehicle generator, front bracket and rear bracket made of aluminum have been popularly employed.
As a clamp nut for mounting the on-vehicle generator onto a stay (for example, hexagon nut), carbon steel material is generally employed.
To prevent the clamp nut from rotating and getting out, in the mentioned conventional on-vehicle generator mounting device, a hexagonal hole is provided through a mounting leg on the front bracket side or rear bracket side so that a part of a hexagonal part coaxially adjacent to a mounting-span-adjusting bush of the clamp nut (normally a hexagonal nut of carbon steel) is in contact with the mounting-span-adjusting bush.
In such a conventional structure, there is a possibility that an aqueous solution of calcium chloride sprayed on the road to act as an anti-freezing agent (snow-removing agent) infiltrates between the hexagonal portion of the clamp nut of carbon steel and the hexagonal hole (hexagonal cylinder part) provided through the mounting leg of aluminum.
Since ionization tendency is different between carbon steel and aluminum, when the aqueous solution of calcium chloride remains for a long time between the hexagonal portion of the clamp nut of carbon steel and the hexagonal hole (hexagonal cylinder part) provided through the mounting leg of aluminum, bimetallic corrosion (contact corrosion with dissimilar metal) and/or crevice corrosion may take place.
When aluminum, being one of the dissimilar metals remains on the surface of the carbon steel in contact therewith, the dissimilar metal comes to corrode due to battery action between the metals. As a result, it is often the case that transfer of rust due to such bimetallic corrosion oxidizes the carbon steel.
That is, when a portion of the mounting leg (hexagonal cylinder part) made of aluminum, being one of dissimilar metals, remains in contact with surface of the clamp nut (carbon steel metal), the dissimilar metal corrodes due to battery action between metals, and the resulting rust corrodes the clamp nut.
In the above-mentioned conventional on-vehicle generator mounting device, once the hexagonal part of the clamp nut rusts, the hexagonal shape finally comes to be round due to corrosion, loosing the contact face between the hexagonal part of the clamp nut and the hexagonal hole (hexagonal cylinder part) provided through the mounting leg. As a result, a problem exists in that the generator is rendered unable to be mounted and removed due to slip of the mounting bolt with which the clamp nut is screw-engaged.
Moreover, because of a complete tubular shape (for example, cylindrical shape) of the mounting-span-adjusting bush, another problem exists in that the aqueous solution of calcium chloride remains in the cylindrical portion of the mounting-span-adjusting bush, resulting in serious corrosion.